1. Field of the Invention
In general, the present invention relates to the structures of blades that move in a waving pattern for moving fluids such as air or water. More particularly, the present invention relates to blades that have airfoils or hydrofoils that include at least one section that becomes deformed by the fluid being moved.
2. Prior Art Description
Hand fans and similar waving fans have been in existence since the dawn of human history. Waving fans are traditionally a piece of flat material that is waved back and forth to displace air and cause movement in the air. The flat piece of material is typically a piece of paperboard or a piece of fabric supported by a frame. When waved through the air, the material acts as a fan blade and moves the air to cause a slight wind.
Although traditional waving fans are simple, they are not highly efficient at moving air. When traditional waving fans are moved through the air, the fans displace the air in a variety of directions. Only a portion of the air displaced by the fan moves in the direction desired. Most of the air is moved in a direction of little benefit to the person waving the fan.
In the art of airfoil design and hydrofoil design for waving blades, there have been numerous design improvements that were intended to improve the efficiency of waving blades. Many of these prior art improvements involve using a flexible material in the foil structure that can catch and displace more air or water. Such prior art blade configurations are exemplified by U.S. Pat. No. 359,374 to Wright and the large family of patents owned by Peter T. McCarthy as exemplified by U.S. Pat. No. 7,601,041.
In such prior art designs, waving blades are provided that contain areas of flexible material. As the blade waves through a fluid, the flexible material stretches to hold and displace more of the fluid. However, the displacement of the fluid is not directed in any one particular direction. The fluid is evenly displaced around the periphery of the blade. As a result, more power is needed to move the blade through the fluid. The net efficiency of the blade configuration remains relatively constant. The blade merely becomes more effective because it moves more air or water. However, the blade configuration does not become more efficient. Much of the fluid that is displaced by the blade is displaced in directions and vertices that serve no useful purpose in propulsion. Consequently, although prior art blades with flexible sections are powerful, they require a greater amount of power to wave. The net efficiency does not change significantly.
A need therefore exists for a blade configuration that efficiently directs that material away from the blade in a useful controlled direction while catching more air or water. This need is met by the present invention as described and claimed below.